The present invention relates to the fabrication of three-dimensional (3D) objects from computer-aided design (CAD) models using layered deposition systems. In particular, the present invention relates to methods for modifying the geometries of thin-wall regions of CAD models.
A layered deposition system is used to build a 3D object from a CAD model (e.g., STL data) in a layer-by-layer manner by depositing a flowable build material onto a substrate in an x-y plane. The build material is deposited as a sequence of roads from a movable deposition head, where the deposited roads solidify to previously deposited build material. The position of the deposition head relative to the substrate is then incremented along a z-axis (perpendicular to the x-y plane), and the process is repeated multiple times to form a 3D object resembling the CAD model.
Movement of the deposition head with respect to the substrate is performed under computer control, in accordance with build data that represents the 3D object. The build data is obtained by slicing the CAD model of the 3D object into multiple horizontally sliced layers. Each sliced layer typically includes one or more polylines that define the geometry of the sliced layer. Each polyline is defined by multiple primary vertices interconnected with linear segments, where each primary vertex is a coordinate point in the x-y plane that represents a point of angular deflection between a pair of the linear segments. Based on the polylines, the host computer then generates one or more tool paths for depositing roads of build material for each sliced layer.
CAD models are typically capable of describing the geometries of 3D objects in greater detail than what layered deposition systems are capable of reproducing. As a result, CAD models may include geometries that create undesirable results, such as overfill conditions, during build operations. One particular geometry that may result in an overfill condition is a thin-wall region, where the wall thickness of the 3D object falls within a range that is greater than the width of a single tool path, but is less than the combined widths of a pair of adjacent tool paths. As such, there is a need for techniques to modify the geometries of thin-wall regions to reduce the risk of creating overfill conditions when building 3D objects with layered deposition systems.